Bobbin for sewing machine

ABSTRACT

A bobbin for a sewing machine which is rotatably disposed in a rotary shell device of the machine to supply and under thread when performing a sewing operation, comprises of winding shaft separately inserted onto a fixed shaft of the rotary shuttle and on which the under thread is substantially wound, a first flange integrally formed at one end of the winding shaft, a second flange integrally formed at the other end of the winding shaft, and a partition flange forming a first winding portion between the first flange and the partition flange and forming a second winding portion between the second flange and the partition flange, a plurality of saw-toothed protrusions being formed at an entire outer circumference of the partition flange, and the protrusions having a linear sidewall that is oriented in a radial direction of the partition flange.

TECHNICAL FIELD

The present invention relates to a sewing machine, and moreparticularly, a bobbin for a sewing machine, in which an under thread isstably pulled out without entanglement or cut of the under thread.

BACKGROUND ART

Generally, a sewing machine, as shown in FIG. 1, has a rotary shuttledevice for supplying an under thread. The rotary shuttle devicecomprises an outer shuttle which is disposed at a driving shaft 1rotatably connected to a power generating unit, an inner shuttle 3 whichis received in the outer shuttle 2, a bobbin 4 which is received in theinner shuttle 3 and on which the under thread is wound, and a bobbincase 5 for receiving the bobbin 4. The bobbin 4 is comprised with acylindrical winding shaft 4 a on which the under thread is wound, and aflange 4 b which is fixed to both end of the winding shaft 4 a torestrict a winding amount of the under thread.

However, a maximum amount or a maximum thickness of the under threadsubstantially wound on the bobbin 4 is set to a maximum amount that theunder thread wound around a descending point of a sewing needle is notcontacted with the sewing needle during a sewing operation. In aconvention bobbin, an amount of the under thread wound on the bobbin isvery much restricted due to a reason set forth above. Therefore, since auser or an operator has to frequently replace an empty bobbin with a newone, there is a problem that the efficiency in a sewing operation islowered.

Recently, in order to solve the problem of the conventional bobbin,i.e., be capable of winding a much more amount of the under thread onthe bobbin, as shown in FIG. 2, there has been proposed a bobbin 6 inwhich a winding region of the under thread is divided into two portions.The bobbin 6 having two winding regions is provided with a first flange6 b having a relatively large diameter which is formed at one end of awinding shaft 6 a, and a second flange 6 c having a relatively smalldiameter which is formed at the other end of the winding shaft 6 a.Particularly, at a center portion of the winding shaft 6 a, there isformed a partition flange 7. A trough portion 7 a and a ridge portion 7b are alternately formed at an outer circumference of the partitionflange 7 so that the under thread facilely passes over the partitionflange 7. Between the first flange 6 b and the partition flange 7, thereis formed a first winding portion 8 a on which a relatively large amountof the under thread is wound. Between the second flange 6 c and thepartition flange 7, there is formed a second winding portion 8 b onwhich a relatively small amount of the under thread is wound.

As described above, a reason why the amount of the under thread wound oneach winding portion 8 a, 8 b is different is that the wound amount ofthe under thread is restricted by the a plurality of trough portions 7 aand ridge portions 7 b formed at the partition flange 7 as well as awidth or height of each flange 6 b, 6 c formed at both ends of thewinding shaft 6 a.

In the bobbin having the partition flange at the center portion thereof,the wound amount of the under thread is somewhat increased. However,there are also some problems. The problems will be described below.

FIG. 2b is a perspective view showing a state that an under thread ispulled out of the conventional bobbin of FIG. 2a. An “A” designates theunder thread passed over from the second winding portion 8 b to thefirst winding portion 8 a. A portion, over which the under thread ispassed, is correspondent to a boundary portion between the rough portion7 a and the ridge portion 7 b. However, it is not consistent. In thissituation, before the under thread wound on one winding region iscompletely pulled out and the winding region is then changed to theother winding region beyond the partition flange during the sewingoperation, the under thread in the state of “A” may be previouslyslipped off from the trough portion or the ridge portion of thepartition flange in an arrow direction due to rotation of the bobbin andthen changed in a state of “B”. If the under thread is previouslyslipped off, the slipped under thread is not deviated from the bobbinfor a time period as long as a length of the slipped under thread andthus entangled with other under thread which is continuously pulled out.As the result, the under thread is not normally supplied to the sewingregion. The under thread will be cut by such phenomenon in the end.Accordingly, the sewing operation is stopped, thereby loweringworkability and also reducing the quality of a sewn product.

DISCLOSURE OF THE INVENTION

Therefore, it is an object of the present invention to provide a bobbinfor a sewing machine, which is capable of preventing an under threadfrom being entangled or cut when being pulled out of the bobbin.

It is other object of the present invention to provide a bobbin for asewing machine, which is capable of preventing an under thread frombeing previously slipped off when the under thread passes over apartition flange between a first winding portion and a second windingportion.

To accomplish the above objects and advantages, there is provided abobbin for a sewing machine comprising a winding shaft which isseparatably inserted onto a fixing shaft of the rotary shuttle deviceand on which the under thread is substantially wound, a first flangewhich is integrally formed at one end of the winding shaft, a secondflange which is integrally formed at the other end of the winding shaftand a partition flange for forming a first winding portion between thefirst flange and the partition flange and a second winding portionbetween the second flange and the partition flange, characterized inthat a plurality of trough portions and ridge portions are alternatelyformed at an entire outer circumference of the partition flange, each ofthe trough portions and the ridge portions has the same gradient eachother, and a side portion is formed at both sides of each trough portionto prevent the under thread from being previously slipped.

BRIEF DESCRIPTION OF THE DRAWINGS

The above object, other features and advantages of the present inventionwill become more apparent by describing the preferred embodiment thereofwith reference to the accompanying drawings, in which:

FIG. 1 is an exploded perspective view of a conventional rotary shuttledevice for a sewing machine;

FIG. 2a is a perspective view of a conventional bobbin;

FIG. 2b is a perspective view showing a state that an under thread ispulled out of the conventional bobbin of FIG. 2a;

FIG. 3 is a perspective view of a bobbin for a sewing machine accordingto a first embodiment of the present invention;

FIG. 4 is a cross-sectional view showing a state that a thread is woundon the bobbin of FIG. 3;

FIGS. 5a to 5 c are sectional-views showing a state that the thread ispulled out;

FIG. 6 is a perspective view of a bobbin for a sewing machine accordingto a second embodiment of the present invention; and

FIG. 7 is a perspective view showing a state that the under thread iscaught on a partition flange of the bobbin for the sewing machine of thefirst embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, preferred embodiments of the present invention will be described indetail with reference to the annexed drawings.

FIG. 3 is a perspective view of a bobbin for a sewing machine accordingto a first embodiment of the present invention, and FIG. 4 is across-sectional view showing a state that a thread is wound on thebobbin of FIG. 3, a bobbin for a sewing machine according to the presentinvention basically has two winding portions for winding an underthread. That is, the bobbin is removably inserted onto a fixing shaft(not shown) of a rotary shuttle device and has a cylindrical windingshaft 10 on which the under thread is substantially wound. At one end ofthe winding shaft 10, there is integrally formed a first flange 12having a relatively large diameter. And at the other end of the windingshaft 10, there is integrally formed a second flange 14 having a smallerdiameter than that of the first flange 12. Further, a partition flange16 is integrally formed at a place between the first and second flange12, 14 formed at both ends of the winding shaft 10. Therefore, due tothe partition flange 16, between the first flange 12 and the partitionflange 16 is formed a first winding portion 18 on which a relativelymuch more amount of under thread is wound, and between the second flange14 and the partition flange 16 is formed a second winding portion 20 onwhich a relatively less amount of under thread is wound.

Herein, the first winding portion 18 is defined as a region on which therelatively more amount of under thread is wound. The second wind portion20 is defined as a region on which the relatively less amount of underthread is wound and a sewing needle is reciprocated up and down. Ofcourse, a maximum amount of the under thread wound on the second windingportion 20 is set to an amount of the thread that is not contacted withthe maximally descended sewing needle. This is to prevent the underthread from being damaged or cut by the sewing needle.

Particularly, a plurality of trough portions 22 and ridge portions 24are alternately formed along an entire outer circumference of thepartition flange 16 provided at a place of the winding shaft 10. Each ofthe trough portions 22 and the ridge portions 24 has the same curvatureor gradient each other. In addition, the number of the trough portions22 is the same as that of the ridge portions 24. For example, thepartition flange 16 is formed with 4 to 12 trough portions 22 and ridgeportions 24, preferably 6 to 12 trough portions 22 and ridge portions24, and more preferably 8 trough portions 22 and ridge portions 24.

Moreover, a side portion 22 a is served as a connecting portion betweenthe trough portion 22 and the ridge portion 24 to restrict a size of thetrough portion 22 and the ridge portion 24. Preferably, the side portion22 a is form in the shape of a linear line directed in acounterclockwise direction. This is to prevent the under thread frombeing previously slipped from the trough portion 22. That is, after theunder thread is completely pulled out of the first winding portion 18,the under thread is temporally supported to prevent the under threadfrom being previously slipped from one of the trough portions 22 of thepartition flange 16. Then, the under thread is slipped off at a desiredposition and time.

Meanwhile, FIG. 6 is a perspective view of the bobbin of the sewingmachine according to a second embodiment of the present invention. Thebobbin in the embodiment is proposed to solve a problem that may beoccurred. The bobbin has a partition flange 26 integrally formed betweena first flange 12 and a second flange 14. On the entire outercircumference of the partition flange 26, there are formed a pluralityof saw-toothed protrusions 34. Each of the saw-toothed protrusions 34has a linear sidewall 32 a that is orientated in a radial direction ofthe partition flange 26. Preferably, the saw-toothed protrusion 34 isformed in the shape of an arc, or may be formed in the shape of an linerline or a curved line.

Hereinafter, an operating mode of the bobbin for the sewing machineaccording to the first embodiment of the present invention is describedin detain with reference to FIGS. 5a to 5 c.

The under thread is wound on the bobbin in a prescribed method using athread winding device or a winder. The under thread T is wound on thesecond winding portion 20, and passes one of the trough portions 22 ofthe partition flange 16, and then wound on the first winding portion 18.

In this situation, if the sewing operation is started, the under threadwound on the first winding portion 18 of the bobbin is pulled out, whilebeing rotated in an opposite direction to a wound direction of the underthread. After the under thread T is completely pulled out of the firstwinding portion 18, the under thread goes over the trough portion 22 ofthe partition flange 16 and then is pulled out of the second windingportion 20. At this time, while the bobbin is continuously rotated, theunder thread is maintained on the trough portion 22 by the side portion22 a of the trough portion 22 without slipping of the under thread fromthe trough portion 22. Only when the under thread is pulled out towardthe sewing region with a desired tensile force, the under thread goesover the second winding portion 20 and is then pulled out, therebypreventing the under thread from being previously slipped and thuscompletely preventing an extra portion of the under thread T which isnot supplied to the sewing region from being entangled with the underthread successively pulled out. Therefore, the under thread can besupplied to the sewing region in a prescribed tensile force and speed.Herein, the extra portion is corresponding to the under thread from thewinding shaft of the first winding portion 18 to an outmost portion ofthe second winding portion 20.

Meanwhile, the bobbin of the second embodiment is operated similarly tothat of the first embodiment. However, there is a differencetherebetween as follows.

FIG. 7 a perspective view showing a state that the under thread iscaught on a partition flange of the bobbin for the sewing machine of thefirst embodiment of the present invention. In case the under thread isloosened due to pause of the sewing operation, etc., and the loosenedunder thread is caught on a sidewall 22 a, as shown in FIG. 7, and thenthe bobbin is rotated in an arrow direction to which the under thread isreleased, the caught under thread may be cut or tangled.

The second embodiment of the present is provided to solve the aboveproblem. The partition flange 26 of the second embodiment has thesaw-toothed protrusions which are protruded in only one direction towhich the under thread is wound. Therefore, it is completely preventedthat the under thread is cut or tangled.

Accordingly, the under thread pulled out of the bobbin is passed throughthe bobbin case in an optimal direction and tensile force without anydamage or cut of the under thread, and then supplied to the sewingregion, thereby facilely performing the sewing operation.

According to the bobbin for the sewing machine according to the presentinvention, when the under thread wound on the bobbin is pulled out ofthe first winding portion and then goes over the second winding portion,it is prevented that the under thread is previously slipped from thetrough portion of the partition flange and entangled with the underthread successively pulled out and also the under thread is cut by theentanglement, thereby improving reliability and economy.

Moreover, since the under thread is continuously supplied withoutstopping, it is also prevented that the sewing operation is stopped,thereby improving workability.

While the present invention has been described in detail, those skilledin the art will appreciate that various modifications and substitutionscan be made thereto without departing from the spirit and scope of thepresent invention as set forth in the appended claims.

What is claimed is:
 1. The bobbin for a sewing machine, which isrotatably disposed in a rotary shuttle device of the sewing machine tosupply an under thread when performing a sewing operation, comprising awinding shaft which is separately inserted onto a fixing shaft of therotary shuttle device and on which the under thread is substantiallywound, a first flange which is integrally formed at one end of thewinding shaft, a second flange which is integrally formed at the otherend of the winding shaft, and a partition flange for forming a firstwinding portion between the first flange and the partition flange andforming a second winding portion between the second flange and thepartition flange, wherein a plurality of saw-toothed protrusions isformed at an entire outer circumference of the partition flange, and theprotrusions has a linear sidewall that is orientated in a radialdirection of the partition flange.